Abstract

Transforming growth factor-beta (TGF-β) drives the development of immature LC from hematopoietic progenitor cells and shapes the cells functions. Here I showed that two LC model cells, MuLC and MDLC, used exchangeably in the research, differ significantly in their phenotype and immune responses. Discrepancies between these models were specifically visible during stimulation with type-I IFN, where MuLC failed to up-regulate ISG levels. Yet both MuLC and MDLC demonstrated low susceptibility to HIV-1 infection, even in the absence of SAMHD-1. This post-entry restriction was conferred by the action of TGF-β on differentiation cells as indicated by our study. Indeed, in the absence of TGF-β supplementation, derived cells showed MDDC phenotype related to high susceptibility of the cells to HIV-1 infection during co-infection with SIV-Vpx. Additionally blocking of the TGF-β signalling, reversed the restrictive phenotype of LC. Importantly this pattern was also confirmed in skin extracted real epidermal LC versus dermal DC, suggesting that SAMHD-1-independent restriction activity operates in TGF-β derived cells. Accordingly to PCR analysis virus replication in LC is interrupted prior to integration, suggesting the role of additional restriction factors at early stages of virus infection or lack of essential viral dependency factors such as dNTPs. Interestingly maturation of MDLC with a synthetic bacterial triacylated lipopeptide or TNF-alpha significantly increased their susceptibility to HIV-1 infection, which may explain why HIV-1 acquisition is increased during co-infection with other STIs. In summary, our study strongly supports the action of SAMHD-1-independent HIV-1 restriction mechanisms in LC. A better understanding of the balance between HIV-1 restriction and propagation from LC to CD4+ T cells may help in the development of new microbicides or vaccines to curb HIV-1 infection at its earliest stages.